A simple mains installation

[Theo]

Before I go to a lot of expense I am asking for the opinions of the resident electrical experts to ensure that what I have is safe:

 

1. Sockets down both sides of the boat. Starboard: 3 doubles, Port: 2 doubles in the cabin and one in a locker near the bow, just abaft the gas locker. This socket is weatherproof and is for running the freezer. Plus one additional socket to the bedroom. IE 3 circuits.

 

2. Sterling 1800W MSW inverter.

 

3. 13A plug fused at 13A feeding a 4 way multiblock screwed to the bulkhead. Each circuit in plugged into the multiblock via a 13A plug each fused at 5A.

 

4. I very rarely use shore power but on the occasions when I do I unplug the multiblock and plug it into the shoreline via a 13A extension socket plugged into the usual 15A blue socket.

 

No blocking diodes yet. In view of the fact that I will be plugging into shore power only once or twice a year, do I need them? I rather think that I do in case my needs change.

 

Please tell me if this is a bad system.

 

All the best

 

Nick

[ChrisPy]

no mention of an RCBO?

 

apparently no earthing to the hull?

 

it seems you are unaware of the basic safety requirements for connecting mains into a boat.

 

PLEASE PLEASE ask a competent boat electrician to advise you.

[Alastair]

Theo, you MUST have an rcd on the system. You MUST earth the system. If you don't understand what an RCD is, or how to earth your wiring, then I suggest you hunt out a friendly electrician and get them to do the work on your boat.

[Gary Peacock]

If it's down to cost we have just started supplying inverters from Ring Automotive they do a 2000w modified sine wave for about £200.00 details HERE

 

You can find the rest of the bits you might need HERE

 

Yet again if you aren't confident to do it don't attempt it!

[Theo]

Theo, you MUST have an rcd on the system. You MUST earth the system. If you don't understand what an RCD is, or how to earth your wiring, then I suggest you hunt out a friendly electrician and get them to do the work on your boat.

Is a "powerblocker" RCD on the socket to the multiblock sufficient?Nick

no mention of an RCBO? apparently no earthing to the hull? it seems you are unaware of the basic safety requirements for connecting mains into a boat. PLEASE PLEASE ask a competent boat electrician to advise you.

That is sorted. Forgot to mention it.Nick

[ChrisPy]

Is a "powerblocker" RCD on the socket to the multiblock sufficient?

Theo, there are no adequate regulations applicable for mains installations on boats.

However there are several standards (for example the ISO for mains AC on boats).

Seriously, if you want to go this route please read up on the subject before you make any decisions. There are so many resources available, some free, others not costing a lot.

It is more about a competent person installing and then testing a complete safe system. It is not only about having a breaker plug in the circuit.

As a starter I suggest you look at

http://www.tb-training.co.uk/MarineE11.htm...S%20ELECTRICITY

[smileypete]

Is a "powerblocker" RCD on the socket to the multiblock sufficient?NickThat is sorted. Forgot to mention it.Nick

 

I would feed the whole lot with a 'garage consumer unit' which usually comes with an RCD and 16A breaker.

 

Plug that into the inverter with a round socket/plug combo, then when using the shoreline just unplug the inverter and plug the shoreline in instead.

 

If you do want to plug a trailing socket/extension lead into the shoreline, I'd make sure it has a permanent weatherproof 'inline' RCD.

 

BTW when you plug into a shoreline, is the shoreline itself always RCD protected, eg always at your 'home' mooring where there's an RCD on the supply?

 

cheers,

Pete.

Edited September 13, 2007 by smileypete

[ChrisPy]

Please be aware that if one cable between the substation and your inlet is wired incorrectly you will have reverse polarity and the neutral will be live.

That may defeat your protective devices.

[Theo]

Please be aware that if one cable between the substation and your inlet is wired incorrectly you will have reverse polarity and the neutral will be live.

That may defeat your protective devices.

 

 

Ah. Useful advice, that. I will have to measure the pd between my "neutral" and earth every time I connect up in a different location. How many people have discovered this to be a problem?

 

Thanks for all the suggestions. I will have a good look at the web sites and decide if I am competent to do it. I have a good theoretical background but less practical experience.

 

Nick

Edited September 13, 2007 by Theo
To add a bit...

[ChrisPy]

Ah. Useful advice, that. I will have to measure the pd between my "neutral" and earth every time I connect up in a different location. How many people have discovered this to be a problem?

 

Thanks for all the suggestions. I will have a good look at the web sites and decide if I am competent to do it. I have a good theoretical background but less practical experience.

 

Nick

Sarcasm is fine, Nick, goes straight over my head, but we're talking safety here. That is why you should have double pole switching and an incorrect polarity indicator light.

 

Electrical engineering and good practice is mainly about protection systems. You do need to understand how they work before you design and install any mains system in your boat.

Edited September 13, 2007 by chris polley

[smileypete]

Please be aware that if one cable between the substation and your inlet is wired incorrectly you will have reverse polarity and the neutral will be live.

That may defeat your protective devices.

 

'may' isn't particulary helpful here...

 

It won't defeat an RCD or a double pole circuit breaker.

 

A 'socket tester' plug from Maplins or somewhere like that will show up reverse polarity and some other faults too.

 

Edit:

 

Chris, where did you get your double pole 16A MCBs from?

 

cheers,

Pete.

Edited September 13, 2007 by smileypete

[Theo]

Sarcasm is fine, Nick, goes straight over my head, but we're talking safety here. That is why you should have double pole switching and an incorrect polarity indicator light.Electrical engineering and good practice is mainly about protection systems. You do need to understand how they work before you design and install any mains system in your boat.

Isn't it odd how things written come out in entirely that wrong way. It was not until I read your mild rebuke and re read my comment that I realised that it did sound very sarcastic. It was not meant to be, at least not very much, perhaps!Right-ho. Being serious. Double pole switches. It is clear what they do. Is the incorrect polarity light something like a neon and its series resistor connected between neutral and earth? Perhaps I just need to read the WWW as you advised.Oh, yes, and really not being sarcastic, this is a genuine question: Is a Sterling inverter going to have a single phase output or two phase? I imagine that it will be single phase since everyone fits normal single pole switched sockets. And does it have some sort of RCD protection built in?Nick

no mention of an RCBO? apparently no earthing to the hull? it seems you are unaware of the basic safety requirements for connecting mains into a boat. PLEASE PLEASE ask a competent boat electrician to advise you.

Is and RCBO the same as an RCD? If not could you enlighten me? Edited September 13, 2007 by Theo
omited leters

[smileypete]

Hi,

 

Thinking about it, a garage consumer unit with RCD and single pole MCBs is quite a good combination.

 

You can isolate the circuit with the double pole RCD. (Good idea to test the RCD with the test button in doing so)

 

Any earth fault will trip the RCD.

 

Any live-neutral overload will trip the MCB.

 

So, in my humbel opinion extra double pole switching and double pole MCBs don't provide additional benefit.

 

cheers,

Pete.

[Scotty]

Is and RCBO the same as an RCD? If not could you enlighten me?

An RCBO is a combination of RCD & MCB in one breaker

 

They have the advantage of giving separate RCD protection to a single circuit which can be tripped and reset without disturbing other circuits.

They can be fiddly or messy to install in a small consumer unit though.

Edited September 13, 2007 by Scotty

[DHutch]

Yeah, i mean basically what you after is the shoreline to come in, then after as short a line as possable, a garage type consumer unit.

- Which will typical consist of an MCBO, to cover residual current faults, and nominally over current of the whole following system.

- Then one or more MCBs to cover over current of the varous circuits coming out of the box. Posably only the one for the ring main.

- We also have a dedicated MCB for the battery charger, and a third for the mains lighting on the boat. (big strip light in the enigineroom).

- Then the system needs to be earthed to the hull, idealy at a seperate, but geographicaly close, point to the 12v systems earth bonding.

 

Then you can also fit 'polarity reverse' and 'feed live'indicators to your consumer unit. Which is something i aim to do shortly on ours.

 

 

Daniel

[chris w]

............Any earth fault will trip the RCD.

 

Note that the RCD will only trip if the hull is bonded to mains earth.

 

Chris

[Guest]

Note that the RCD will only trip if the hull is bonded to mains earth.

 

Chris

Very true and very important.

[smileypete]

Note that the RCD will only trip if the hull is bonded to mains earth.

 

Sorry, but that's absolute rubbish!

 

Yes, really!

 

You're following me around again...!

 

Pete.

[chris w]

Pete

 

If the RCD is not connected to earth it will have zero effect because it won't be able to distinguish any current imbalance on the live and neutral wires (which is how RCD's function). Without the mains earth being bonded to the hull your boat will be "floating" both in the water sense and in the electrical sense.

 

Further, anyone stepping on board when an earth fault has occurred on the boat will receive a full mains shock because they WILL be earthed. Similarly if you shake hands with someone on the shore while you are standing on the boat (and when an earth fault has occurred), you will both receive a full (possibly fatal) mains shock.

 

I repeat an RCD will do NOTHING if your mains earth is not bonded to the hull.

 

Work it out Pete. If you touch the live wire whilst on-board, without a hull earth bond, how is any current going to flow through you back to the sub-station? It's not, there's no path. You won't feel a thing (and neither will the RCD) because you are floating at 240v. (Compare this to birds sitting on a 33,000V pylon live wire. They feel nothing because there is no path to earth).

 

However, touch someone on shore and you may be entering the pearly gates together.

 

An earth bond to the hull is essential or else there is no point in having an RCD. It won't trip otherwise.

 

Chris

 

PS: if my mate Gibbo is around he will confirm this too

Edited September 13, 2007 by chris w

[bottle]

Sorry, but that's absolute rubbish!

 

Yes, really!

 

You're following me around again...!

 

Pete.

 

Proof required, please.

[Alastair]

Pete

 

If the RCD is not connected to earth it will have zero effect because it won't be able to distinguish any current imbalance on the live and neutral wires (which is how RCD's function). Without the mains earth being bonded to the hull your boat will be "floating" both in the water sense and in the electrical sense.

 

Further, anyone stepping on board when an earth fault has occurred on the boat will receive a full mains shock because they WILL be earthed. Similarly if you shake hands with someone on the shore while you are standing on the boat (and when an earth fault has occurred), you will both receive a full (possibly fatal) mains shock.

 

I repeat an RCD will do NOTHING if your mains earth is not bonded to the hull.

 

Work it out Pete. If you touch the live wire whilst on-board, without a hull earth bond, how is any current going to flow through you back to the sub-station? It's not, there's no path. You won't feel a thing (and neither will the RCD) because you are floating at 240v. (Compare this to birds sitting on a 33,000V pylon live wire. They feel nothing because there is no path to earth).

 

However, touch someone on shore and you may be entering the pearly gates together.

 

An earth bond to the hull is essential or else there is no point in having an RCD. It won't trip otherwise.

 

Chris

 

PS: if my mate Gibbo is around he will confirm this too

 

What happens if there is an isolation transformer in the circuit? Is it that the earth goes back to the transformer, ditto neutral, so the RCD will be tripped by the difference between the earth and neutral on board?

 

If a boat earth is strapped to the hull, wouldn't a live/neutral fault trigger some flow via the hull and water to earth?

[chris w]

What happens if there is an isolation transformer in the circuit? Is it that the earth goes back to the transformer, ditto neutral, so the RCD will be tripped by the difference between the earth and neutral on board?

 

Correct - the hull is connected to neutral on the BOAT side of the IT (just like shore earth is connected to neutral at the sub-station). Shore earth is connected to the frame of the IT. The RCD will still be tripped by any difference between LIVE and NEUTRAL currents.

If a boat earth is strapped to the hull, wouldn't a live/neutral fault trigger some flow via the hull and water to earth?

 

It may - but would you risk your life or the lives of any kids on board on that being a satisfactory and reliable path?

Edited September 14, 2007 by chris w

[smileypete]

Gawd!!!

 

An RCD just detects any imbalance in the current flow between live and neutral. It doesn't need or have an earth connection.

 

If there is leakage from the live or neutral connections downstream of the RCD, this will create an imbalance between live and neutral currents and trip the RCD.

 

Bottle, if you want proof, why not do some research into how RCDs work?

 

Some of the other stuff Chris has posted is absolute rubbish too, but I can't keep up with it

 

cheers,

Pete.

[chris w]

Gawd!!!

 

An RCD just detects any imbalance in the current flow between live and neutral. It doesn't need or have an earth connection.

 

If there is leakage from the live or neutral connections downstream of the RCD, this will create an imbalance between live and neutral currents and trip the RCD.

 

Bottle, if you want proof, why not do some research into how RCDs work?

 

Some of the other stuff Chris has posted is absolute rubbish too, but I can't keep up with it

 

cheers,

Pete.

 

Pete

 

I am afraid to say that you are talking complete bollox about RCDs and making some very dangerous statements..................

 

You state above:

 

1. An RCD just detects any imbalance in the current flow between live and neutral. I AGREE

 

2. It doesn't need or have an earth connection. There needs to be an earth connection or otherwise there would be no imbalance. If you touched the live connector with your hand, the current would NOT flow through you if there were no earth and so there would be no imbalance. You would be floating at mains potential (ie: there would be no live or neutral just a potential between the 2 conductors). As in an isolated shaver socket...... touch either wire and you will not get a shock..........touch both at the same time and you will.

 

How do you think birds survive sitting on wires that carry a potential (relative to earth) of 330,000v? Because there is no path to earth

 

3. If there is leakage from the live or neutral connections downstream of the RCD, this will create an imbalance between live and neutral currents and trip the RCD. Only if a portion of the live current can flow to earth and get back to the substation without going through the neutral. Otherwise there is no imbalance and hence no RCD trip.

 

You really are being a dickhead Pete - I used to respect your posts but this dangerous, lack-of-knowledge crap could put lives at risk.

Chris

Edited September 14, 2007 by chris w

[Scotty]

I repeat an RCD will do NOTHING if your mains earth is not bonded to the hull.

 

Work it out Pete. If you touch the live wire whilst on-board, without a hull earth bond, how is any current going to flow through you back to the sub-station? It's not, there's no path. You won't feel a thing (and neither will the RCD) because you are floating at 240v. (Compare this to birds sitting on a 33,000V pylon live wire. They feel nothing because there is no path to earth).

 

However, touch someone on shore and you may be entering the pearly gates together.

 

An earth bond to the hull is essential or else there is no point in having an RCD. It won't trip otherwise.

Chris,

Surely when you touch someone on shore you create the imbalance the RCD requires to trip and nobody dies

 

 

I'm more concerned with the Neutral/Earth being bonded together,

surely then the RCD can't detect earth leakage when you find yourself as a conductor between Live and Hull